Game 1Unit 19 of 201 hr learning time
The Title
The game gets a front door: GLOAMING on a black void, PRESS SPACE, a dusk chime — built hardwired first, then done properly: the boot-time setup becomes init_game, and beginning becomes a thing the game can do, not just a thing that happens once.
95% of Gloaming
Boot Gloaming and you’re simply in the square, mid-story: the wisp already gathering, the clock already running, no name spoken, no breath taken. Every game you’ve ever loaded knows better — there’s a screen with a name on it, a moment that belongs to you, and a deliberate act of beginning. This unit builds that front door twice: once the obvious way, which works and teaches the pieces — and once the right way, which restructures the whole program and hands Unit 20 the key it needs.
Milestone 1 — a door, hardwired
Everything the title needs already exists. The screen is clear_bitmap, the blackout LDIR from the lose screen, and two print_string calls — GLOAMING at row 8, PRESS SPACE at row 14, white on a black void. (Sparse is the aesthetic and the budget: on this machine, restraint photographs as atmosphere.) The sound is a fourth phrase for the beeper — chime_dusk, two cold tolls on a low A, then the game’s little motif far off. And the key is a promise kept: Unit 5’s try-this had you read SPACE — $7FFE, bit 0 — “fifteen units early”. Tonight it’s load-bearing.
So wire it the way anyone would first: at boot, draw the title, chime, and sit in a little loop reading SPACE until it drops — then fall through into the setup and the game we’ve always had.
Step 1: title screen, chime, and an inline wait for SPACE
+65-7
| 39 | 39 | STATE_LOSE equ 3 ; night falls — the game is lost | |
| 40 | 40 | | |
| 41 | 41 | SPEAKER equ %00010000 ; port $FE bit 4 — the beeper's one bit | |
| 42 | + | | |
| 43 | + | TITLE_COL equ 12 ; GLOAMING, centred | |
| 44 | + | PROMPT_COL equ 10 ; PRESS SPACE, centred | |
| 45 | + | TITLE_ROW equ 8 | |
| 46 | + | PROMPT_ROW equ 14 | |
| 42 | 47 | | |
| 43 | 48 | START_COL equ 15 ; where the lamplighter begins | |
| 44 | 49 | START_ROW equ 11 | |
| ... | |||
| 48 | 53 | KEYS_OP equ $DFFE ; half-row P O I U Y — bits 1 and 0 | |
| 49 | 54 | KEYS_Q equ $FBFE ; half-row Q W E R T — bit 0 is Q | |
| 50 | 55 | KEYS_A equ $FDFE ; half-row A S D F G — bit 0 is A | |
| 56 | + | KEYS_SPACE equ $7FFE ; half-row SPACE SYM M N B — bit 0 | |
| 51 | 57 | | |
| 52 | 58 | start: | |
| 53 | 59 | ; --- the border goes black — the night beyond the square --- | |
| 54 | 60 | ; Port $FE bits 0-2 set the BORDER colour. A = 0 = black. | |
| 55 | 61 | ld a, 0 | |
| 56 | 62 | out ($FE), a | |
| 63 | + | ; the front door, hardwired (this step only): show the title, | |
| 64 | + | ; chime, and wait here for SPACE before the game exists | |
| 65 | + | call draw_title_screen | |
| 66 | + | im 1 | |
| 67 | + | ei | |
| 68 | + | call chime_dusk ; after EI — the rests need the interrupt | |
| 69 | + | .twait: | |
| 70 | + | halt | |
| 71 | + | ld bc, KEYS_SPACE | |
| 72 | + | in a, (c) | |
| 73 | + | bit 0, a | |
| 74 | + | jr nz, .twait | |
| 57 | 75 | xor a | |
| 58 | 76 | ld (lit_count), a | |
| 59 | 77 | ld a, LIVES | |
| ... | |||
| 114 | 132 | call draw_draught | |
| 115 | 133 | ld a, STATE_PLAY | |
| 116 | 134 | ld (game_state), a | |
| 117 | - | | |
| 118 | - | ; --- start the heartbeat --- | |
| 119 | - | ; IM 1: every 50 Hz frame interrupt calls the ROM's handler. | |
| 120 | - | ; EI: let it. HALT then sleeps until the next frame arrives, | |
| 121 | - | ; so the loop below beats exactly once per frame. | |
| 122 | - | im 1 | |
| 123 | - | ei | |
| 124 | 135 | | |
| 125 | 136 | main_loop: | |
| 126 | 137 | halt | |
| ... | |||
| 234 | 245 | call beep | |
| 235 | 246 | ld b, $28 ; E6 | |
| 236 | 247 | ld c, $51 | |
| 248 | + | jp beep | |
| 249 | + | | |
| 250 | + | chime_dusk: ; two cold tolls, then the motif far off | |
| 251 | + | ld b, $84 ; A4 | |
| 252 | + | ld c, $F7 | |
| 253 | + | call beep | |
| 254 | + | ld b, 10 | |
| 255 | + | call rest | |
| 256 | + | ld b, $84 ; A4 | |
| 257 | + | ld c, $F7 | |
| 258 | + | call beep | |
| 259 | + | ld b, 13 | |
| 260 | + | call rest | |
| 261 | + | ld b, $92 ; E5 | |
| 262 | + | ld c, $A4 | |
| 263 | + | call beep | |
| 264 | + | ld b, 4 | |
| 265 | + | call rest | |
| 266 | + | ld b, $9D ; C5 | |
| 267 | + | ld c, $CF | |
| 237 | 268 | jp beep | |
| 238 | 269 | | |
| 239 | 270 | ; rest — B frames of silence. Musical time rides the heartbeat: the | |
| ... | |||
| 287 | 318 | | |
| 288 | 319 | ; draw_win_screen — lift the lamplighter off the board (restore his | |
| 289 | 320 | ; cell: the eighth lamp, lit, comes out of the buffer), then say it. | |
| 321 | + | ; draw_title_screen — sparse and suggestive: a black void, the name, | |
| 322 | + | ; the invitation. Everything else is left to the imagination, which | |
| 323 | + | ; is both the aesthetic and the budget. | |
| 324 | + | draw_title_screen: | |
| 325 | + | call clear_bitmap | |
| 326 | + | ld hl, $5800 | |
| 327 | + | ld de, $5801 | |
| 328 | + | ld (hl), %00000000 | |
| 329 | + | ld bc, 767 | |
| 330 | + | ldir | |
| 331 | + | ld hl, title_text | |
| 332 | + | ld b, TITLE_ROW | |
| 333 | + | ld c, TITLE_COL | |
| 334 | + | call print_string | |
| 335 | + | ld hl, prompt_text | |
| 336 | + | ld b, PROMPT_ROW | |
| 337 | + | ld c, PROMPT_COL | |
| 338 | + | call print_string | |
| 339 | + | ret | |
| 340 | + | | |
| 290 | 341 | draw_win_screen: | |
| 291 | 342 | call restore_under | |
| 292 | 343 | ld hl, win_text | |
| ... | |||
| 1121 | 1172 | defb %01111110 | |
| 1122 | 1173 | defb %00111100 | |
| 1123 | 1174 | defb %00000000 | |
| 1175 | + | | |
| 1176 | + | title_text: | |
| 1177 | + | defb "GLOAMING" | |
| 1178 | + | defb $FF | |
| 1179 | + | prompt_text: | |
| 1180 | + | defb "PRESS SPACE" | |
| 1181 | + | defb $FF | |
| 1124 | 1182 | | |
| 1125 | 1183 | win_text: | |
| 1126 | 1184 | defb "THE NIGHT IS HELD" |
The complete step 1 program
; Gloaming — Unit 19: The Title
; Cumulative build; every step runs on its own. Narrative: the unit page.
; Sparse and suggestive; press a key to begin — setup becomes the title's job.
org 32768
COBBLE equ %00000001 ; PAPER black (0), INK blue (1) — dark ground
WALL equ %00001111 ; PAPER blue (1), INK white (7) — pale stone
WALL_BIT equ 3 ; the attribute bit that says "this is wall"
LAMP_ATTR equ %01000111 ; BRIGHT, PAPER black, INK white — his own light
LAMP_UNLIT equ %00000101 ; cold cyan INK on black PAPER — bit 3
; clear, so a lamp reads as floor
LAMP_LIT equ %01000110 ; BRIGHT yellow INK on black — a held flame
DRAUGHT_ATTR equ %01000101 ; the wisp: BRIGHT cyan on black — cold light
LIVES equ 3
LIFE_PIP equ %01010000 ; a life: BRIGHT red PAPER — a small ember
LIFE_BASE equ $5800 + 28 ; row 0, right of the ledge — three cells
DRAUGHT_SPEED equ 16 ; frames between the wisp's steps
DRAUGHT_COL0 equ 28 ; the corner the dark enters from
DRAUGHT_ROW0 equ 4
PIP_UNLIT equ %00101000 ; a cold pip: cyan PAPER, a solid block
PIP_LIT equ %01110000 ; a warm pip: BRIGHT yellow PAPER
PIP_BASE equ $5800 + 12 ; row 0, column 12 — the HUD ledge,
; eight cells, centred over the square
NUM_LAMPS equ 8
MSG_ATTR equ %01000111 ; message text: bright white on black
MSG_ROW equ 11
LOSE_COL equ 10 ; centres the eleven characters
WIN_COL equ 7 ; centres the seventeen characters
FONT equ $3C00 ; the ROM font, addressed so that
; ASCII x 8 lands on the right glyph
STATE_PLAY equ 1
STATE_WIN equ 2 ; the night is held — the game is won
STATE_LOSE equ 3 ; night falls — the game is lost
SPEAKER equ %00010000 ; port $FE bit 4 — the beeper's one bit
TITLE_COL equ 12 ; GLOAMING, centred
PROMPT_COL equ 10 ; PRESS SPACE, centred
TITLE_ROW equ 8
PROMPT_ROW equ 14
START_COL equ 15 ; where the lamplighter begins
START_ROW equ 11
PLAYER_REPEAT equ 6 ; frames between steps while a key is held
GATHER equ 120 ; frames the dark gathers before its first step
KEYS_OP equ $DFFE ; half-row P O I U Y — bits 1 and 0
KEYS_Q equ $FBFE ; half-row Q W E R T — bit 0 is Q
KEYS_A equ $FDFE ; half-row A S D F G — bit 0 is A
KEYS_SPACE equ $7FFE ; half-row SPACE SYM M N B — bit 0
start:
; --- the border goes black — the night beyond the square ---
; Port $FE bits 0-2 set the BORDER colour. A = 0 = black.
ld a, 0
out ($FE), a
; the front door, hardwired (this step only): show the title,
; chime, and wait here for SPACE before the game exists
call draw_title_screen
im 1
ei
call chime_dusk ; after EI — the rests need the interrupt
.twait:
halt
ld bc, KEYS_SPACE
in a, (c)
bit 0, a
jr nz, .twait
xor a
ld (lit_count), a
ld a, LIVES
ld (lives), a
; --- place the lamplighter ---
; His position is data. Everything that draws him reads it.
ld a, START_COL
ld (lamp_col), a
ld a, START_ROW
ld (lamp_row), a
; --- and, in the far corner, something else ---
ld a, DRAUGHT_COL0
ld (draught_col), a
ld a, DRAUGHT_ROW0
ld (draught_row), a
; the dark gathers before its first step — a beat to read
; the square before the hunt begins
ld a, GATHER
ld (draught_timer), a
xor a
ld (player_timer), a
; --- wipe the canvas ---
; The bitmap ($4000-$57FF) is the pixel layer; whatever was on
; screen before us still lives there. Zero it so only our
; attribute colours show.
call clear_bitmap
; --- texture the ground ---
; Blit the cobble stipple into every cell's bitmap, rows 1-23.
; The attributes will colour these pixels in a moment.
call fill_ground
; --- wash in the cobbles ---
; Seed the first attribute cell, point DE one cell ahead, and
; let LDIR cascade the byte through all 768 cells.
ld hl, $5800
ld de, $5801
ld (hl), COBBLE
ld bc, 767
ldir
call warm_walls
call paint_buildings
; --- brick the walls ---
; Now that the wall cells are painted, fill_walls can read the
; map back and lay brick wherever the wall bit is set.
call fill_walls
call draw_pips
call draw_lives
call draw_lamps
; save what he is about to stand on, BEFORE the first draw
call save_under
call draw_lamp
call save_draught
call draw_draught
ld a, STATE_PLAY
ld (game_state), a
main_loop:
halt
; the state gate: only PLAY beats the game forward — any
; other state leaves the screen exactly as it stands
ld a, (game_state)
cp STATE_PLAY
jr z, .do_play
jr main_loop ; WIN or LOSE — the screen holds
.do_play:
call play_step
jr main_loop
; play_step — one beat of the game: ask the keyboard.
play_step:
call player_step
; contact can end the game mid-frame — if it did, stop here
ld a, (game_state)
cp STATE_PLAY
ret nz
call draught_step
ld a, (game_state)
cp STATE_PLAY
ret nz
; the win check, at the only beat the count can have changed
ld a, (lit_count)
cp NUM_LAMPS
ret nz
call draw_win_screen
call fanfare_held
ld a, STATE_WIN
ld (game_state), a
ret
; ----------------------------------------------------------------------------
; warm_walls — the square's edge, one attribute write per cell; the
; colour is no longer a constant but the wall_ramp entry for how many
; lamps are lit. Same painting loop as ever — only where C comes from
; has changed.
; ----------------------------------------------------------------------------
warm_walls:
ld a, (lit_count)
ld e, a
ld d, 0
ld hl, wall_ramp
add hl, de
ld c, (hl) ; the byte every wall cell gets
; the top wall: row 1 is 32 cells in a row from $5820
; (row 0 is kept back — it becomes the HUD later)
ld hl, $5820
ld b, 32
.wt:
ld (hl), c
inc hl
djnz .wt
; the bottom wall: row 23, 32 cells from $5AE0
ld hl, $5AE0
ld b, 32
.wb:
ld (hl), c
inc hl
djnz .wb
; the side walls: column 0 and column 31 of rows 1-23.
; Write the row's first cell, hop 31 cells to its last,
; then step a full row (32) down — 23 times.
ld hl, $5820
ld b, 23
.ws:
ld (hl), c
push hl
ld de, 31
add hl, de
ld (hl), c
pop hl
ld de, 32
add hl, de
djnz .ws
ret
; ----------------------------------------------------------------------------
; The beeper. One bit on port $FE: set it, wait, clear it, wait — a
; square wave by hand. C is the half-period (pitch: bigger is lower),
; B the number of cycles (duration). DI while it sounds: the 50 Hz
; interrupt would stretch random half-periods and buzz the tone.
; ----------------------------------------------------------------------------
beep:
di
.bcyc:
ld a, SPEAKER
out ($FE), a
ld a, c
.bd1:
dec a
jr nz, .bd1
xor a
out ($FE), a
ld a, c
.bd2:
dec a
jr nz, .bd2
djnz .bcyc
ei
ret
blip_lit: ; a rising third — the lamp catches
ld b, $17 ; C6
ld c, $67
call beep
ld b, $28 ; E6
ld c, $51
jp beep
chime_dusk: ; two cold tolls, then the motif far off
ld b, $84 ; A4
ld c, $F7
call beep
ld b, 10
call rest
ld b, $84 ; A4
ld c, $F7
call beep
ld b, 13
call rest
ld b, $92 ; E5
ld c, $A4
call beep
ld b, 4
call rest
ld b, $9D ; C5
ld c, $CF
jp beep
; rest — B frames of silence. Musical time rides the heartbeat: the
; gaps between notes are counted in HALTs, not busy-loops.
rest:
halt
djnz rest
ret
fanfare_held: ; THE NIGHT IS HELD — a rising run
ld b, $83 ; C5
ld c, $CF
call beep
ld b, 3
call rest
ld b, $A5 ; E5
ld c, $A4
call beep
ld b, 3
call rest
ld b, $C4 ; G5
ld c, $8A
call beep
ld b, 3
call rest
ld b, $FF ; C6, held — B only counts to 255,
ld c, $67
call beep
ld b, $FF ; so hold it by sounding it twice
ld c, $67
jp beep
sting_nightfall: ; NIGHT FALLS — two steps down, then dark
ld b, $53 ; E5
ld c, $A4
call beep
ld b, 4
call rest
ld b, $49 ; D5
ld c, $B8
call beep
ld b, 4
call rest
ld b, $DC ; A4, long — the night settles on it
ld c, $F7
jp beep
; ----------------------------------------------------------------------------
; Screens.
; ----------------------------------------------------------------------------
; draw_win_screen — lift the lamplighter off the board (restore his
; cell: the eighth lamp, lit, comes out of the buffer), then say it.
; draw_title_screen — sparse and suggestive: a black void, the name,
; the invitation. Everything else is left to the imagination, which
; is both the aesthetic and the budget.
draw_title_screen:
call clear_bitmap
ld hl, $5800
ld de, $5801
ld (hl), %00000000
ld bc, 767
ldir
ld hl, title_text
ld b, TITLE_ROW
ld c, TITLE_COL
call print_string
ld hl, prompt_text
ld b, PROMPT_ROW
ld c, PROMPT_COL
call print_string
ret
draw_win_screen:
call restore_under
ld hl, win_text
ld b, MSG_ROW
ld c, WIN_COL
call print_string
ret
; draw_lose_screen — the whole attribute table goes black: every lamp,
; every wall, every warm cell, gone in one LDIR. Then the words.
draw_lose_screen:
ld hl, $5800
ld de, $5801
ld (hl), %00000000
ld bc, 767
ldir
ld hl, lose_text
ld b, MSG_ROW
ld c, LOSE_COL
call print_string
ret
; ----------------------------------------------------------------------------
; clear_bitmap — zero the pixel layer, $4000-$57FF, with the same
; seed-and-cascade LDIR idiom the cobble wash uses.
; ----------------------------------------------------------------------------
clear_bitmap:
ld hl, $4000
ld de, $4001
ld (hl), 0
ld bc, 6143
ldir
ret
; ----------------------------------------------------------------------------
; player_step — the keys become movement. Each direction key edits a
; TARGET position (tcol, trow) — a proposal, not yet a move — so it
; can be vetoed before it becomes real. Then the move commits: leave
; the old cell, take the new one, draw.
; ----------------------------------------------------------------------------
player_step:
; --- propose: the target starts where he stands ---
ld a, (lamp_col)
ld (tcol), a
ld a, (lamp_row)
ld (trow), a
; The held-key gate: the first press steps at once, then one
; step every PLAYER_REPEAT frames. Releasing every direction
; key re-arms the instant first step, so taps stay crisp.
ld bc, KEYS_OP
in a, (c)
cpl
and %00000011
ld e, a
ld bc, KEYS_Q
in a, (c)
cpl
and %00000001
or e
ld e, a
ld bc, KEYS_A
in a, (c)
cpl
and %00000001
or e
jr nz, .held
xor a
ld (player_timer), a
ret
.held:
ld a, (player_timer)
or a
jr z, .stepnow
dec a
ld (player_timer), a
ret
.stepnow:
ld a, PLAYER_REPEAT
ld (player_timer), a
ld bc, KEYS_OP
in a, (c)
bit 1, a ; O — a zero bit is a pressed key
jr z, .pleft
bit 0, a ; P, same half-row
jr z, .pright
ld bc, KEYS_Q
in a, (c)
bit 0, a ; Q
jr z, .pup
ld bc, KEYS_A
in a, (c)
bit 0, a ; A
jr z, .pdown
ret ; nothing held — nothing to do
.pleft:
ld hl, tcol
dec (hl)
jr .pmove
.pright:
ld hl, tcol
inc (hl)
jr .pmove
.pup:
ld hl, trow
dec (hl)
jr .pmove
.pdown:
ld hl, trow
inc (hl)
.pmove:
; The veto: ask the target cell's attribute whether it's wall.
; NZ means brick — the proposal dies here and he stays put.
ld a, (trow)
ld b, a
ld a, (tcol)
ld c, a
call wall_at
ret nz
; and the mirror rule: he cannot step onto the wisp either
ld a, (tcol)
ld hl, draught_col
cp (hl)
jr nz, .pcommit
ld a, (trow)
ld hl, draught_row
cp (hl)
jr nz, .pcommit
call lose_life ; walking into the cold costs the same
ret
.pcommit:
; --- commit: restore, step, save, draw — in that order ---
call restore_under
ld a, (tcol)
ld (lamp_col), a
ld a, (trow)
ld (lamp_row), a
call save_under
; light it where it lives: while he covers the lamp, its truth
; is the buffer — rewrite the saved attribute, and restore will
; paint the lamp back lit when he leaves
ld a, (under_lamp + 8)
cp LAMP_UNLIT
jr nz, .pdrawn
ld a, LAMP_LIT
ld (under_lamp + 8), a
call light_pip
call blip_lit
call warm_walls
.pdrawn:
call draw_lamp
ret
; ----------------------------------------------------------------------------
; fill_ground — the cobble stipple. Not decoration: the stipple is what
; makes ground-state changes visible later, when the game starts
; recolouring these pixels. Rows 1-23 (row 0 is the HUD).
; ----------------------------------------------------------------------------
fill_ground:
ld b, 1 ; rows 1-23 (row 0 is the HUD)
.fgr:
ld c, 0
.fgc:
ld de, cobble_tex
call blit_tex
inc c
ld a, c
cp 32
jr c, .fgc
inc b
ld a, b
cp 24
jr c, .fgr
ret
; fill_walls — brickwork. Driven by the wall attribute bit, so anything
; painted as wall — now or later in the game — gets its brick for free:
; the map itself decides where the brick goes.
fill_walls:
ld b, 1
.fwr:
ld c, 0
.fwc:
push bc
call attr_addr_cr
bit WALL_BIT, (hl)
pop bc
jr z, .fwn
ld de, brick_tex
call blit_tex
.fwn:
inc c
ld a, c
cp 32
jr c, .fwc
inc b
ld a, b
cp 24
jr c, .fwr
ret
; blit_tex — write the 8-byte texture at DE into cell (C, B)'s bitmap.
; scr_addr_cr finds the cell's first pixel row; INC H steps down the
; other seven, 256 bytes apart.
blit_tex:
push bc
call scr_addr_cr
ld b, 8
.bt:
ld a, (de)
ld (hl), a
inc de
inc h
djnz .bt
pop bc
ret
cobble_tex:
defb %10000010
defb %00000000
defb %00001000
defb %00000000
defb %00100001
defb %00000000
defb %00010000
defb %00000000
brick_tex:
; mortar courses with staggered verticals — dusk-lit stone
defb %00001000
defb %00001000
defb %00001000
defb %11111111
defb %10000000
defb %10000000
defb %10000000
defb %11111111
; ----------------------------------------------------------------------------
; draught_step — the hunt. One rule: step one cell along the axis with
; the greater distance to the lamplighter (ties go sideways). No walls,
; no vetoes — the wisp is not of the town, and stone means nothing to it.
; ----------------------------------------------------------------------------
draught_step:
ld a, (draught_timer)
dec a
ld (draught_timer), a
ret nz
ld a, DRAUGHT_SPEED
ld (draught_timer), a
; the dark hunts the lamplighter's own flame
ld a, (lamp_col)
ld (seek_col), a
ld a, (lamp_row)
ld (seek_row), a
.chase:
; step one cell along the axis with the greater distance
; (ties go sideways) — the night is 4-connected, like the
; lamplighter
ld a, (draught_col)
ld (dtcol), a
ld a, (draught_row)
ld (dtrow), a
ld a, (seek_col)
ld hl, draught_col
sub (hl)
jp p, .absc
neg
.absc:
ld d, a ; D = |dc|
ld a, (seek_row)
ld hl, draught_row
sub (hl)
jp p, .absr
neg
.absr:
cp d ; |dr| vs |dc|
jr z, .tie
jr c, .horiz
jr .vert
.tie:
ld a, d
or a
ret z ; already on the light
jr .horiz
.horiz:
ld a, (seek_col)
ld hl, draught_col
cp (hl)
jr c, .hleft
ld a, (hl)
inc a
ld (dtcol), a
jr .contact
.hleft:
ld a, (hl)
dec a
ld (dtcol), a
jr .contact
.vert:
ld a, (seek_row)
ld hl, draught_row
cp (hl)
jr c, .vup
ld a, (hl)
inc a
ld (dtrow), a
jr .contact
.vup:
ld a, (hl)
dec a
ld (dtrow), a
.contact:
; never step ONTO the lamplighter: adjacent is as close as
; the night comes. Two movers, two buffers — and one cell
; can only ever be under one of them.
ld a, (dtcol)
ld hl, lamp_col
cp (hl)
jr nz, .dmove
ld a, (dtrow)
ld hl, lamp_row
cp (hl)
jr nz, .dmove
call lose_life ; the touch, priced
ret
.dmove:
call restore_draught
ld a, (dtcol)
ld (draught_col), a
ld a, (dtrow)
ld (draught_row), a
call save_draught
call draw_draught
ret
; paint_buildings — walk the rectangle table: each entry is col, row,
; width, height; $FF ends the list. Every cell inside a rectangle gets
; the WALL attribute — and because fill_walls textures by the wall bit,
; the brickwork arrives without another line of drawing code.
paint_buildings:
ld hl, bldg_data
.pb:
ld a, (hl)
cp $FF
ret z
ld c, a ; col
inc hl
ld b, (hl) ; row
inc hl
ld d, (hl) ; width
inc hl
ld e, (hl) ; height
inc hl
push hl
.pbrow:
push bc
push de
.pbcol:
push bc
push de
call attr_addr_cr
ld (hl), WALL
pop de
pop bc
inc c
dec d
jr nz, .pbcol
pop de
pop bc
inc b
dec e
jr nz, .pbrow
pop hl
jr .pb
bldg_data:
defb 5, 5, 4, 3
defb 23, 5, 4, 3
defb $FF
; ----------------------------------------------------------------------------
; lose_life — the price of the touch: one ember out, and either a
; fresh start or the fall of night.
; ----------------------------------------------------------------------------
lose_life:
ld a, (lives)
dec a
ld (lives), a
ld e, a
ld d, 0
ld hl, LIFE_BASE
add hl, de
ld (hl), COBBLE ; the ember at the new count goes out
ld a, (lives)
or a
jr z, .gone
; a life left: the lamplighter returns to the start cell
call restore_under
ld a, START_COL
ld (lamp_col), a
ld a, START_ROW
ld (lamp_row), a
call save_under
call draw_lamp
; the taking costs the night its reach — the wisp recoils to
; the far corner, so every life buys a whole fresh chase
; (leaving it beside the respawn made a catch strip every
; life in seconds once the draught learnt to hunt)
call restore_draught
ld a, DRAUGHT_COL0
ld (draught_col), a
ld a, DRAUGHT_ROW0
ld (draught_row), a
ld a, DRAUGHT_SPEED
ld (draught_timer), a
call save_draught
call draw_draught
ret
.gone:
call draw_lose_screen
call sting_nightfall
ld a, STATE_LOSE
ld (game_state), a
ret
; ----------------------------------------------------------------------------
; print_string / print_char — the machine's own letters. The Spectrum
; keeps its font in ROM: eight bytes per character, and FONT is chosen
; so that ASCII code x 8 + FONT is the glyph's address. Each character
; is drawn like any cell: attribute first, eight rows down the cell.
; ----------------------------------------------------------------------------
print_string:
.ps:
ld a, (hl)
cp $FF
ret z
push hl
push bc
call print_char
pop bc
pop hl
inc hl
inc c
jr .ps
print_char:
ld l, a
ld h, 0
add hl, hl
add hl, hl
add hl, hl
ld de, FONT
add hl, de
ex de, hl
push de
call attr_addr_cr
ld (hl), MSG_ATTR
call scr_addr_cr
pop de
ld b, 8
.pc:
ld a, (de)
ld (hl), a
inc de
inc h
djnz .pc
ret
; ----------------------------------------------------------------------------
; light_pip / draw_pips / draw_lives.
; ----------------------------------------------------------------------------
; light_pip — warm the next pip along and count the lamp. lit_count is
; the index of the pip to light AND the number of lamps lit so far —
; read it for the address, then step it.
light_pip:
ld a, (lit_count)
ld e, a
ld d, 0
inc a
ld (lit_count), a
ld hl, PIP_BASE
add hl, de
ld (hl), PIP_LIT
ret
; draw_pips — the tally row: one cell per lamp on the HUD ledge, all
; cold to start. A pip is pure attribute — no glyph, just a block of
; PAPER — so the row costs eight bytes of screen and no bitmap at all.
draw_pips:
ld hl, PIP_BASE
ld b, NUM_LAMPS
ld a, PIP_UNLIT
.dp:
ld (hl), a
inc hl
djnz .dp
ret
; draw_lives — three embers on the ledge's right shoulder.
draw_lives:
ld hl, LIFE_BASE
ld b, LIVES
ld a, LIFE_PIP
.dlv:
ld (hl), a
inc hl
djnz .dlv
ret
; ----------------------------------------------------------------------------
; draw_lamps — walk the position table: col, row pairs, $FF to finish.
; Placement is data; the drawing code neither knows nor cares how many
; lamps the town has tonight.
; ----------------------------------------------------------------------------
draw_lamps:
ld hl, lamp_data
.next:
ld a, (hl)
cp $FF
ret z
ld c, a
inc hl
ld b, (hl)
inc hl
push hl
call draw_lantern
pop hl
jr .next
; draw_lantern — an unlit lamp into cell (C, B): cold cyan attribute,
; then the lantern glyph down the cell like any texture.
draw_lantern:
call attr_addr_cr
ld (hl), LAMP_UNLIT
call scr_addr_cr
ld de, lantern
ld b, 8
.dlt:
ld a, (de)
ld (hl), a
inc de
inc h
djnz .dlt
ret
; ----------------------------------------------------------------------------
; scr_addr_cr — HL = bitmap address of cell (C, B)'s first pixel row.
; The row's top two bits pick the third of the screen (H), its bottom
; three become L's top bits, and the column fills L's low five.
; ----------------------------------------------------------------------------
scr_addr_cr:
ld a, b
and %00011000 ; the third (row bits 4-3) ...
or %01000000 ; ... under the screen base $40xx
ld h, a
ld a, b
and %00000111 ; the char row within the third ...
rrca ; ... rotated into bits 7-5
rrca
rrca
or c ; the column in bits 4-0
ld l, a
ret
; attr_addr_cr — HL = attribute address of cell (C, B):
; $5800 + row*32 + col, the row shifted up five times.
attr_addr_cr:
ld a, b
ld l, a
ld h, 0
add hl, hl
add hl, hl
add hl, hl
add hl, hl
add hl, hl
ld de, $5800
add hl, de
ld a, c
ld e, a
ld d, 0
add hl, de
ret
; wall_at — is cell (C, B) wall? The answer is already on the screen:
; every wall cell's attribute has WALL_BIT set, so one bit-test of
; attribute memory is the whole collision system. NZ = wall.
wall_at:
call attr_addr_cr
bit WALL_BIT, (hl)
ret
; ----------------------------------------------------------------------------
; The lamplighter's save / restore / draw.
; ----------------------------------------------------------------------------
; pos_bc — the lamplighter's cell into (C, B), read fresh from the data.
pos_bc:
ld a, (lamp_row)
ld b, a
ld a, (lamp_col)
ld c, a
ret
; save_under — copy the nine bytes of his cell into the buffer: eight
; bitmap rows, then the attribute. Runs as he ARRIVES, before the
; draw — so the buffer always holds true ground, never him.
save_under:
call pos_bc
call scr_addr_cr
ld de, under_lamp
ld b, 8
.su:
ld a, (hl)
ld (de), a
inc de
inc h
djnz .su
call pos_bc
call attr_addr_cr
ld a, (hl)
ld (under_lamp + 8), a
ret
; restore_under — the same nine bytes back the other way: the ground
; returns exactly as it was. Runs as he LEAVES, while the position
; still points at the old cell.
restore_under:
call pos_bc
call scr_addr_cr
ld de, under_lamp
ld b, 8
.ru:
ld a, (de)
ld (hl), a
inc de
inc h
djnz .ru
call pos_bc
call attr_addr_cr
ld a, (under_lamp + 8)
ld (hl), a
ret
draw_lamp:
; his colour first: the cell's attribute becomes his own —
; bright white on the black, his own light about him
call pos_bc
call attr_addr_cr
ld (hl), LAMP_ATTR
; then his shape, eight bytes down the cell like any texture
call pos_bc
call scr_addr_cr
ld de, lamplighter
ld b, 8
.dl:
ld a, (de)
ld (hl), a
inc de
inc h
djnz .dl
ret
; ----------------------------------------------------------------------------
; The draught's save / restore / draw — the lamplighter's engine, twice.
; Same loops, same nine-byte contract, its own buffer and its own
; position: two movers can share a world but never a buffer.
; ----------------------------------------------------------------------------
dpos_bc:
ld a, (draught_row)
ld b, a
ld a, (draught_col)
ld c, a
ret
save_draught:
call dpos_bc
call scr_addr_cr
ld de, under_draught
ld b, 8
.sd:
ld a, (hl)
ld (de), a
inc de
inc h
djnz .sd
call dpos_bc
call attr_addr_cr
ld a, (hl)
ld (under_draught + 8), a
ret
restore_draught:
call dpos_bc
call scr_addr_cr
ld de, under_draught
ld b, 8
.rd:
ld a, (de)
ld (hl), a
inc de
inc h
djnz .rd
call dpos_bc
call attr_addr_cr
ld a, (under_draught + 8)
ld (hl), a
ret
draw_draught:
call dpos_bc
call attr_addr_cr
ld (hl), DRAUGHT_ATTR
call dpos_bc
call scr_addr_cr
ld de, draught_glyph
ld b, 8
.dd:
ld a, (de)
ld (hl), a
inc de
inc h
djnz .dd
ret
; ----------------------------------------------------------------------------
; Data.
; ----------------------------------------------------------------------------
game_state:
defb STATE_PLAY
wall_ramp:
; The square warms in the game's own vocabulary: the stone
; stays dusk-blue; the lamplight catches the mortar first
; (ink white -> yellow), then the whole face glows BRIGHT.
; Never magenta — warmth is yellow here, not red-shifted blue.
defb %00001111 ; dusk stone, white mortar
defb %00001111
defb %00001111
defb %00001110 ; the mortar warms — yellow ink
defb %00001110
defb %00001110
defb %01001110 ; the stone catches the glow — BRIGHT
defb %01001110
defb %01110000 ; all eight lit: the square aglow —
; warm yellow stone, only at the win
lamp_data:
defb 4, 3
defb 27, 3
defb 9, 7
defb 22, 7
defb 6, 15
defb 25, 15
defb 13, 20
defb 18, 20
defb $FF
lamp_col:
defb START_COL
lamp_row:
defb START_ROW
tcol:
defb 0
trow:
defb 0
lit_count:
defb 0
lives:
defb LIVES
draught_col:
defb 28
draught_row:
defb 4
draught_timer:
defb 16
player_timer:
defb 0
seek_col:
defb 0
seek_row:
defb 0
dtcol:
defb 0
dtrow:
defb 0
under_lamp:
defb 0, 0, 0, 0, 0, 0, 0, 0, 0
under_draught:
defb 0, 0, 0, 0, 0, 0, 0, 0, 0
lamplighter:
defb %00111100
defb %00111100
defb %00011000
defb %01111110
defb %00011000
defb %00011000
defb %00100100
defb %01000010
lantern:
defb %00011000
defb %00100100
defb %01111110
defb %01111110
defb %01011010
defb %01111110
defb %01111110
defb %00111100
draught_glyph:
defb %00000000
defb %00111100
defb %01111110
defb %11111111
defb %11111111
defb %01111110
defb %00111100
defb %00000000
title_text:
defb "GLOAMING"
defb $FF
prompt_text:
defb "PRESS SPACE"
defb $FF
win_text:
defb "THE NIGHT IS HELD"
defb $FF
lose_text:
defb "NIGHT FALLS"
defb $FF
end start
One ordering detail in the setup rewards attention: the chime is called after im 1 / ei, unlike everything else sound-adjacent so far. Why? Its rests. rest counts silence in HALTs, and HALT waits for an interrupt — call the chime before ei and the first rest waits forever, on a machine that looks perfectly healthy and plays exactly one note. When one subsystem quietly depends on another being switched on, the order of two boot lines becomes a bug you can hear.
What’s wrong with the door
Play from it. Title, chime, SPACE, game — it all works. Now win, and look at where you are: THE NIGHT IS HELD, holding forever. Lose: NIGHT FALLS, forever. The title was real, but it wasn’t a place — it was a preamble, executed once on the way in, unreachable ever after. The deeper problem is structural, and it’s worth saying precisely: “beginning the game” is not a thing this program can do; it’s a thing that happened. The setup code runs once, woven into the boot path, and nothing can ever ask for it again. Unit 20 needs to send you from the end screens back to a title that can start a fresh night — and this shape has no handle to grab.
Milestone 2 — beginning becomes callable
The fix is the last restructure of the module, and not one visible byte changes on screen. Three moves:
- The setup body becomes
init_game— everything from zeroinglit_countto drawing the wisp, lifted whole out ofstartand given a name and aret. Beginning is now a routine. - The title becomes a state.
STATE_TITLEjoins the machine — as state zero, the state thegame_statebyte’s owndefbboots into — andtitle_stepowns the waiting: each frame, read SPACE; on a press,call init_game, switch toSTATE_PLAY. - The loop learns to dispatch. The Unit 15 gate grows into the real thing: TITLE frames go to
title_step, PLAY frames toplay_step, WIN and LOSE hold. Each state now names what a frame means.
Step 2: STATE_TITLE, title_step, and setup becomes init_game
+58-39
| 34 | 34 | FONT equ $3C00 ; the ROM font, addressed so that | |
| 35 | 35 | ; ASCII x 8 lands on the right glyph | |
| 36 | 36 | | |
| 37 | + | STATE_TITLE equ 0 | |
| 37 | 38 | STATE_PLAY equ 1 | |
| 38 | 39 | STATE_WIN equ 2 ; the night is held — the game is won | |
| 39 | 40 | STATE_LOSE equ 3 ; night falls — the game is lost | |
| ... | |||
| 60 | 61 | ; Port $FE bits 0-2 set the BORDER colour. A = 0 = black. | |
| 61 | 62 | ld a, 0 | |
| 62 | 63 | out ($FE), a | |
| 63 | - | ; the front door, hardwired (this step only): show the title, | |
| 64 | - | ; chime, and wait here for SPACE before the game exists | |
| 64 | + | ld a, STATE_TITLE | |
| 65 | + | ld (game_state), a | |
| 65 | 66 | call draw_title_screen | |
| 66 | 67 | im 1 | |
| 67 | 68 | ei | |
| 68 | 69 | call chime_dusk ; after EI — the rests need the interrupt | |
| 69 | - | .twait: | |
| 70 | + | | |
| 71 | + | main_loop: | |
| 70 | 72 | halt | |
| 73 | + | ; the dispatch: each state names what a frame means — the | |
| 74 | + | ; title listens for a beginning, PLAY beats the game forward, | |
| 75 | + | ; WIN and LOSE hold the screen exactly as it stands | |
| 76 | + | ld a, (game_state) | |
| 77 | + | cp STATE_TITLE | |
| 78 | + | jr z, .do_title | |
| 79 | + | cp STATE_PLAY | |
| 80 | + | jr z, .do_play | |
| 81 | + | jr main_loop | |
| 82 | + | .do_title: | |
| 83 | + | call title_step | |
| 84 | + | jr main_loop | |
| 85 | + | .do_play: | |
| 86 | + | call play_step | |
| 87 | + | jr main_loop | |
| 88 | + | | |
| 89 | + | ; ---------------------------------------------------------------------------- | |
| 90 | + | ; title_step — SPACE starts a fresh game. | |
| 91 | + | ; ---------------------------------------------------------------------------- | |
| 92 | + | title_step: | |
| 71 | 93 | ld bc, KEYS_SPACE | |
| 72 | 94 | in a, (c) | |
| 73 | 95 | bit 0, a | |
| 74 | - | jr nz, .twait | |
| 96 | + | ret nz | |
| 97 | + | call init_game | |
| 98 | + | ld a, STATE_PLAY | |
| 99 | + | ld (game_state), a | |
| 100 | + | ret | |
| 101 | + | | |
| 102 | + | ; play_step — one beat of the game: ask the keyboard. | |
| 103 | + | play_step: | |
| 104 | + | call player_step | |
| 105 | + | ; contact can end the game mid-frame — if it did, stop here | |
| 106 | + | ld a, (game_state) | |
| 107 | + | cp STATE_PLAY | |
| 108 | + | ret nz | |
| 109 | + | call draught_step | |
| 110 | + | ld a, (game_state) | |
| 111 | + | cp STATE_PLAY | |
| 112 | + | ret nz | |
| 113 | + | ; the win check, at the only beat the count can have changed | |
| 114 | + | ld a, (lit_count) | |
| 115 | + | cp NUM_LAMPS | |
| 116 | + | ret nz | |
| 117 | + | call draw_win_screen | |
| 118 | + | call fanfare_held | |
| 119 | + | ld a, STATE_WIN | |
| 120 | + | ld (game_state), a | |
| 121 | + | ret | |
| 122 | + | | |
| 123 | + | ; ---------------------------------------------------------------------------- | |
| 124 | + | ; init_game — everything a fresh night needs, gathered from what was | |
| 125 | + | ; the boot sequence. Beginning is a callable thing now. | |
| 126 | + | ; ---------------------------------------------------------------------------- | |
| 127 | + | init_game: | |
| 75 | 128 | xor a | |
| 76 | 129 | ld (lit_count), a | |
| 77 | 130 | ld a, LIVES | |
| ... | |||
| 130 | 183 | call draw_lamp | |
| 131 | 184 | call save_draught | |
| 132 | 185 | call draw_draught | |
| 133 | - | ld a, STATE_PLAY | |
| 134 | - | ld (game_state), a | |
| 135 | - | | |
| 136 | - | main_loop: | |
| 137 | - | halt | |
| 138 | - | ; the state gate: only PLAY beats the game forward — any | |
| 139 | - | ; other state leaves the screen exactly as it stands | |
| 140 | - | ld a, (game_state) | |
| 141 | - | cp STATE_PLAY | |
| 142 | - | jr z, .do_play | |
| 143 | - | jr main_loop ; WIN or LOSE — the screen holds | |
| 144 | - | .do_play: | |
| 145 | - | call play_step | |
| 146 | - | jr main_loop | |
| 147 | - | | |
| 148 | - | ; play_step — one beat of the game: ask the keyboard. | |
| 149 | - | play_step: | |
| 150 | - | call player_step | |
| 151 | - | ; contact can end the game mid-frame — if it did, stop here | |
| 152 | - | ld a, (game_state) | |
| 153 | - | cp STATE_PLAY | |
| 154 | - | ret nz | |
| 155 | - | call draught_step | |
| 156 | - | ld a, (game_state) | |
| 157 | - | cp STATE_PLAY | |
| 158 | - | ret nz | |
| 159 | - | ; the win check, at the only beat the count can have changed | |
| 160 | - | ld a, (lit_count) | |
| 161 | - | cp NUM_LAMPS | |
| 162 | - | ret nz | |
| 163 | - | call draw_win_screen | |
| 164 | - | call fanfare_held | |
| 165 | - | ld a, STATE_WIN | |
| 166 | - | ld (game_state), a | |
| 167 | 186 | ret | |
| 168 | 187 | | |
| 169 | 188 | ; ---------------------------------------------------------------------------- | |
| ... | |||
| 1078 | 1097 | ; ---------------------------------------------------------------------------- | |
| 1079 | 1098 | | |
| 1080 | 1099 | game_state: | |
| 1081 | - | defb STATE_PLAY | |
| 1100 | + | defb STATE_TITLE | |
| 1082 | 1101 | | |
| 1083 | 1102 | wall_ramp: | |
| 1084 | 1103 | ; The square warms in the game's own vocabulary: the stone |
The complete program
; Gloaming — Unit 19: The Title
; Cumulative build; every step runs on its own. Narrative: the unit page.
; Sparse and suggestive; press a key to begin — setup becomes the title's job.
org 32768
COBBLE equ %00000001 ; PAPER black (0), INK blue (1) — dark ground
WALL equ %00001111 ; PAPER blue (1), INK white (7) — pale stone
WALL_BIT equ 3 ; the attribute bit that says "this is wall"
LAMP_ATTR equ %01000111 ; BRIGHT, PAPER black, INK white — his own light
LAMP_UNLIT equ %00000101 ; cold cyan INK on black PAPER — bit 3
; clear, so a lamp reads as floor
LAMP_LIT equ %01000110 ; BRIGHT yellow INK on black — a held flame
DRAUGHT_ATTR equ %01000101 ; the wisp: BRIGHT cyan on black — cold light
LIVES equ 3
LIFE_PIP equ %01010000 ; a life: BRIGHT red PAPER — a small ember
LIFE_BASE equ $5800 + 28 ; row 0, right of the ledge — three cells
DRAUGHT_SPEED equ 16 ; frames between the wisp's steps
DRAUGHT_COL0 equ 28 ; the corner the dark enters from
DRAUGHT_ROW0 equ 4
PIP_UNLIT equ %00101000 ; a cold pip: cyan PAPER, a solid block
PIP_LIT equ %01110000 ; a warm pip: BRIGHT yellow PAPER
PIP_BASE equ $5800 + 12 ; row 0, column 12 — the HUD ledge,
; eight cells, centred over the square
NUM_LAMPS equ 8
MSG_ATTR equ %01000111 ; message text: bright white on black
MSG_ROW equ 11
LOSE_COL equ 10 ; centres the eleven characters
WIN_COL equ 7 ; centres the seventeen characters
FONT equ $3C00 ; the ROM font, addressed so that
; ASCII x 8 lands on the right glyph
STATE_TITLE equ 0
STATE_PLAY equ 1
STATE_WIN equ 2 ; the night is held — the game is won
STATE_LOSE equ 3 ; night falls — the game is lost
SPEAKER equ %00010000 ; port $FE bit 4 — the beeper's one bit
TITLE_COL equ 12 ; GLOAMING, centred
PROMPT_COL equ 10 ; PRESS SPACE, centred
TITLE_ROW equ 8
PROMPT_ROW equ 14
START_COL equ 15 ; where the lamplighter begins
START_ROW equ 11
PLAYER_REPEAT equ 6 ; frames between steps while a key is held
GATHER equ 120 ; frames the dark gathers before its first step
KEYS_OP equ $DFFE ; half-row P O I U Y — bits 1 and 0
KEYS_Q equ $FBFE ; half-row Q W E R T — bit 0 is Q
KEYS_A equ $FDFE ; half-row A S D F G — bit 0 is A
KEYS_SPACE equ $7FFE ; half-row SPACE SYM M N B — bit 0
start:
; --- the border goes black — the night beyond the square ---
; Port $FE bits 0-2 set the BORDER colour. A = 0 = black.
ld a, 0
out ($FE), a
ld a, STATE_TITLE
ld (game_state), a
call draw_title_screen
im 1
ei
call chime_dusk ; after EI — the rests need the interrupt
main_loop:
halt
; the dispatch: each state names what a frame means — the
; title listens for a beginning, PLAY beats the game forward,
; WIN and LOSE hold the screen exactly as it stands
ld a, (game_state)
cp STATE_TITLE
jr z, .do_title
cp STATE_PLAY
jr z, .do_play
jr main_loop
.do_title:
call title_step
jr main_loop
.do_play:
call play_step
jr main_loop
; ----------------------------------------------------------------------------
; title_step — SPACE starts a fresh game.
; ----------------------------------------------------------------------------
title_step:
ld bc, KEYS_SPACE
in a, (c)
bit 0, a
ret nz
call init_game
ld a, STATE_PLAY
ld (game_state), a
ret
; play_step — one beat of the game: ask the keyboard.
play_step:
call player_step
; contact can end the game mid-frame — if it did, stop here
ld a, (game_state)
cp STATE_PLAY
ret nz
call draught_step
ld a, (game_state)
cp STATE_PLAY
ret nz
; the win check, at the only beat the count can have changed
ld a, (lit_count)
cp NUM_LAMPS
ret nz
call draw_win_screen
call fanfare_held
ld a, STATE_WIN
ld (game_state), a
ret
; ----------------------------------------------------------------------------
; init_game — everything a fresh night needs, gathered from what was
; the boot sequence. Beginning is a callable thing now.
; ----------------------------------------------------------------------------
init_game:
xor a
ld (lit_count), a
ld a, LIVES
ld (lives), a
; --- place the lamplighter ---
; His position is data. Everything that draws him reads it.
ld a, START_COL
ld (lamp_col), a
ld a, START_ROW
ld (lamp_row), a
; --- and, in the far corner, something else ---
ld a, DRAUGHT_COL0
ld (draught_col), a
ld a, DRAUGHT_ROW0
ld (draught_row), a
; the dark gathers before its first step — a beat to read
; the square before the hunt begins
ld a, GATHER
ld (draught_timer), a
xor a
ld (player_timer), a
; --- wipe the canvas ---
; The bitmap ($4000-$57FF) is the pixel layer; whatever was on
; screen before us still lives there. Zero it so only our
; attribute colours show.
call clear_bitmap
; --- texture the ground ---
; Blit the cobble stipple into every cell's bitmap, rows 1-23.
; The attributes will colour these pixels in a moment.
call fill_ground
; --- wash in the cobbles ---
; Seed the first attribute cell, point DE one cell ahead, and
; let LDIR cascade the byte through all 768 cells.
ld hl, $5800
ld de, $5801
ld (hl), COBBLE
ld bc, 767
ldir
call warm_walls
call paint_buildings
; --- brick the walls ---
; Now that the wall cells are painted, fill_walls can read the
; map back and lay brick wherever the wall bit is set.
call fill_walls
call draw_pips
call draw_lives
call draw_lamps
; save what he is about to stand on, BEFORE the first draw
call save_under
call draw_lamp
call save_draught
call draw_draught
ret
; ----------------------------------------------------------------------------
; warm_walls — the square's edge, one attribute write per cell; the
; colour is no longer a constant but the wall_ramp entry for how many
; lamps are lit. Same painting loop as ever — only where C comes from
; has changed.
; ----------------------------------------------------------------------------
warm_walls:
ld a, (lit_count)
ld e, a
ld d, 0
ld hl, wall_ramp
add hl, de
ld c, (hl) ; the byte every wall cell gets
; the top wall: row 1 is 32 cells in a row from $5820
; (row 0 is kept back — it becomes the HUD later)
ld hl, $5820
ld b, 32
.wt:
ld (hl), c
inc hl
djnz .wt
; the bottom wall: row 23, 32 cells from $5AE0
ld hl, $5AE0
ld b, 32
.wb:
ld (hl), c
inc hl
djnz .wb
; the side walls: column 0 and column 31 of rows 1-23.
; Write the row's first cell, hop 31 cells to its last,
; then step a full row (32) down — 23 times.
ld hl, $5820
ld b, 23
.ws:
ld (hl), c
push hl
ld de, 31
add hl, de
ld (hl), c
pop hl
ld de, 32
add hl, de
djnz .ws
ret
; ----------------------------------------------------------------------------
; The beeper. One bit on port $FE: set it, wait, clear it, wait — a
; square wave by hand. C is the half-period (pitch: bigger is lower),
; B the number of cycles (duration). DI while it sounds: the 50 Hz
; interrupt would stretch random half-periods and buzz the tone.
; ----------------------------------------------------------------------------
beep:
di
.bcyc:
ld a, SPEAKER
out ($FE), a
ld a, c
.bd1:
dec a
jr nz, .bd1
xor a
out ($FE), a
ld a, c
.bd2:
dec a
jr nz, .bd2
djnz .bcyc
ei
ret
blip_lit: ; a rising third — the lamp catches
ld b, $17 ; C6
ld c, $67
call beep
ld b, $28 ; E6
ld c, $51
jp beep
chime_dusk: ; two cold tolls, then the motif far off
ld b, $84 ; A4
ld c, $F7
call beep
ld b, 10
call rest
ld b, $84 ; A4
ld c, $F7
call beep
ld b, 13
call rest
ld b, $92 ; E5
ld c, $A4
call beep
ld b, 4
call rest
ld b, $9D ; C5
ld c, $CF
jp beep
; rest — B frames of silence. Musical time rides the heartbeat: the
; gaps between notes are counted in HALTs, not busy-loops.
rest:
halt
djnz rest
ret
fanfare_held: ; THE NIGHT IS HELD — a rising run
ld b, $83 ; C5
ld c, $CF
call beep
ld b, 3
call rest
ld b, $A5 ; E5
ld c, $A4
call beep
ld b, 3
call rest
ld b, $C4 ; G5
ld c, $8A
call beep
ld b, 3
call rest
ld b, $FF ; C6, held — B only counts to 255,
ld c, $67
call beep
ld b, $FF ; so hold it by sounding it twice
ld c, $67
jp beep
sting_nightfall: ; NIGHT FALLS — two steps down, then dark
ld b, $53 ; E5
ld c, $A4
call beep
ld b, 4
call rest
ld b, $49 ; D5
ld c, $B8
call beep
ld b, 4
call rest
ld b, $DC ; A4, long — the night settles on it
ld c, $F7
jp beep
; ----------------------------------------------------------------------------
; Screens.
; ----------------------------------------------------------------------------
; draw_win_screen — lift the lamplighter off the board (restore his
; cell: the eighth lamp, lit, comes out of the buffer), then say it.
; draw_title_screen — sparse and suggestive: a black void, the name,
; the invitation. Everything else is left to the imagination, which
; is both the aesthetic and the budget.
draw_title_screen:
call clear_bitmap
ld hl, $5800
ld de, $5801
ld (hl), %00000000
ld bc, 767
ldir
ld hl, title_text
ld b, TITLE_ROW
ld c, TITLE_COL
call print_string
ld hl, prompt_text
ld b, PROMPT_ROW
ld c, PROMPT_COL
call print_string
ret
draw_win_screen:
call restore_under
ld hl, win_text
ld b, MSG_ROW
ld c, WIN_COL
call print_string
ret
; draw_lose_screen — the whole attribute table goes black: every lamp,
; every wall, every warm cell, gone in one LDIR. Then the words.
draw_lose_screen:
ld hl, $5800
ld de, $5801
ld (hl), %00000000
ld bc, 767
ldir
ld hl, lose_text
ld b, MSG_ROW
ld c, LOSE_COL
call print_string
ret
; ----------------------------------------------------------------------------
; clear_bitmap — zero the pixel layer, $4000-$57FF, with the same
; seed-and-cascade LDIR idiom the cobble wash uses.
; ----------------------------------------------------------------------------
clear_bitmap:
ld hl, $4000
ld de, $4001
ld (hl), 0
ld bc, 6143
ldir
ret
; ----------------------------------------------------------------------------
; player_step — the keys become movement. Each direction key edits a
; TARGET position (tcol, trow) — a proposal, not yet a move — so it
; can be vetoed before it becomes real. Then the move commits: leave
; the old cell, take the new one, draw.
; ----------------------------------------------------------------------------
player_step:
; --- propose: the target starts where he stands ---
ld a, (lamp_col)
ld (tcol), a
ld a, (lamp_row)
ld (trow), a
; The held-key gate: the first press steps at once, then one
; step every PLAYER_REPEAT frames. Releasing every direction
; key re-arms the instant first step, so taps stay crisp.
ld bc, KEYS_OP
in a, (c)
cpl
and %00000011
ld e, a
ld bc, KEYS_Q
in a, (c)
cpl
and %00000001
or e
ld e, a
ld bc, KEYS_A
in a, (c)
cpl
and %00000001
or e
jr nz, .held
xor a
ld (player_timer), a
ret
.held:
ld a, (player_timer)
or a
jr z, .stepnow
dec a
ld (player_timer), a
ret
.stepnow:
ld a, PLAYER_REPEAT
ld (player_timer), a
ld bc, KEYS_OP
in a, (c)
bit 1, a ; O — a zero bit is a pressed key
jr z, .pleft
bit 0, a ; P, same half-row
jr z, .pright
ld bc, KEYS_Q
in a, (c)
bit 0, a ; Q
jr z, .pup
ld bc, KEYS_A
in a, (c)
bit 0, a ; A
jr z, .pdown
ret ; nothing held — nothing to do
.pleft:
ld hl, tcol
dec (hl)
jr .pmove
.pright:
ld hl, tcol
inc (hl)
jr .pmove
.pup:
ld hl, trow
dec (hl)
jr .pmove
.pdown:
ld hl, trow
inc (hl)
.pmove:
; The veto: ask the target cell's attribute whether it's wall.
; NZ means brick — the proposal dies here and he stays put.
ld a, (trow)
ld b, a
ld a, (tcol)
ld c, a
call wall_at
ret nz
; and the mirror rule: he cannot step onto the wisp either
ld a, (tcol)
ld hl, draught_col
cp (hl)
jr nz, .pcommit
ld a, (trow)
ld hl, draught_row
cp (hl)
jr nz, .pcommit
call lose_life ; walking into the cold costs the same
ret
.pcommit:
; --- commit: restore, step, save, draw — in that order ---
call restore_under
ld a, (tcol)
ld (lamp_col), a
ld a, (trow)
ld (lamp_row), a
call save_under
; light it where it lives: while he covers the lamp, its truth
; is the buffer — rewrite the saved attribute, and restore will
; paint the lamp back lit when he leaves
ld a, (under_lamp + 8)
cp LAMP_UNLIT
jr nz, .pdrawn
ld a, LAMP_LIT
ld (under_lamp + 8), a
call light_pip
call blip_lit
call warm_walls
.pdrawn:
call draw_lamp
ret
; ----------------------------------------------------------------------------
; fill_ground — the cobble stipple. Not decoration: the stipple is what
; makes ground-state changes visible later, when the game starts
; recolouring these pixels. Rows 1-23 (row 0 is the HUD).
; ----------------------------------------------------------------------------
fill_ground:
ld b, 1 ; rows 1-23 (row 0 is the HUD)
.fgr:
ld c, 0
.fgc:
ld de, cobble_tex
call blit_tex
inc c
ld a, c
cp 32
jr c, .fgc
inc b
ld a, b
cp 24
jr c, .fgr
ret
; fill_walls — brickwork. Driven by the wall attribute bit, so anything
; painted as wall — now or later in the game — gets its brick for free:
; the map itself decides where the brick goes.
fill_walls:
ld b, 1
.fwr:
ld c, 0
.fwc:
push bc
call attr_addr_cr
bit WALL_BIT, (hl)
pop bc
jr z, .fwn
ld de, brick_tex
call blit_tex
.fwn:
inc c
ld a, c
cp 32
jr c, .fwc
inc b
ld a, b
cp 24
jr c, .fwr
ret
; blit_tex — write the 8-byte texture at DE into cell (C, B)'s bitmap.
; scr_addr_cr finds the cell's first pixel row; INC H steps down the
; other seven, 256 bytes apart.
blit_tex:
push bc
call scr_addr_cr
ld b, 8
.bt:
ld a, (de)
ld (hl), a
inc de
inc h
djnz .bt
pop bc
ret
cobble_tex:
defb %10000010
defb %00000000
defb %00001000
defb %00000000
defb %00100001
defb %00000000
defb %00010000
defb %00000000
brick_tex:
; mortar courses with staggered verticals — dusk-lit stone
defb %00001000
defb %00001000
defb %00001000
defb %11111111
defb %10000000
defb %10000000
defb %10000000
defb %11111111
; ----------------------------------------------------------------------------
; draught_step — the hunt. One rule: step one cell along the axis with
; the greater distance to the lamplighter (ties go sideways). No walls,
; no vetoes — the wisp is not of the town, and stone means nothing to it.
; ----------------------------------------------------------------------------
draught_step:
ld a, (draught_timer)
dec a
ld (draught_timer), a
ret nz
ld a, DRAUGHT_SPEED
ld (draught_timer), a
; the dark hunts the lamplighter's own flame
ld a, (lamp_col)
ld (seek_col), a
ld a, (lamp_row)
ld (seek_row), a
.chase:
; step one cell along the axis with the greater distance
; (ties go sideways) — the night is 4-connected, like the
; lamplighter
ld a, (draught_col)
ld (dtcol), a
ld a, (draught_row)
ld (dtrow), a
ld a, (seek_col)
ld hl, draught_col
sub (hl)
jp p, .absc
neg
.absc:
ld d, a ; D = |dc|
ld a, (seek_row)
ld hl, draught_row
sub (hl)
jp p, .absr
neg
.absr:
cp d ; |dr| vs |dc|
jr z, .tie
jr c, .horiz
jr .vert
.tie:
ld a, d
or a
ret z ; already on the light
jr .horiz
.horiz:
ld a, (seek_col)
ld hl, draught_col
cp (hl)
jr c, .hleft
ld a, (hl)
inc a
ld (dtcol), a
jr .contact
.hleft:
ld a, (hl)
dec a
ld (dtcol), a
jr .contact
.vert:
ld a, (seek_row)
ld hl, draught_row
cp (hl)
jr c, .vup
ld a, (hl)
inc a
ld (dtrow), a
jr .contact
.vup:
ld a, (hl)
dec a
ld (dtrow), a
.contact:
; never step ONTO the lamplighter: adjacent is as close as
; the night comes. Two movers, two buffers — and one cell
; can only ever be under one of them.
ld a, (dtcol)
ld hl, lamp_col
cp (hl)
jr nz, .dmove
ld a, (dtrow)
ld hl, lamp_row
cp (hl)
jr nz, .dmove
call lose_life ; the touch, priced
ret
.dmove:
call restore_draught
ld a, (dtcol)
ld (draught_col), a
ld a, (dtrow)
ld (draught_row), a
call save_draught
call draw_draught
ret
; paint_buildings — walk the rectangle table: each entry is col, row,
; width, height; $FF ends the list. Every cell inside a rectangle gets
; the WALL attribute — and because fill_walls textures by the wall bit,
; the brickwork arrives without another line of drawing code.
paint_buildings:
ld hl, bldg_data
.pb:
ld a, (hl)
cp $FF
ret z
ld c, a ; col
inc hl
ld b, (hl) ; row
inc hl
ld d, (hl) ; width
inc hl
ld e, (hl) ; height
inc hl
push hl
.pbrow:
push bc
push de
.pbcol:
push bc
push de
call attr_addr_cr
ld (hl), WALL
pop de
pop bc
inc c
dec d
jr nz, .pbcol
pop de
pop bc
inc b
dec e
jr nz, .pbrow
pop hl
jr .pb
bldg_data:
defb 5, 5, 4, 3
defb 23, 5, 4, 3
defb $FF
; ----------------------------------------------------------------------------
; lose_life — the price of the touch: one ember out, and either a
; fresh start or the fall of night.
; ----------------------------------------------------------------------------
lose_life:
ld a, (lives)
dec a
ld (lives), a
ld e, a
ld d, 0
ld hl, LIFE_BASE
add hl, de
ld (hl), COBBLE ; the ember at the new count goes out
ld a, (lives)
or a
jr z, .gone
; a life left: the lamplighter returns to the start cell
call restore_under
ld a, START_COL
ld (lamp_col), a
ld a, START_ROW
ld (lamp_row), a
call save_under
call draw_lamp
; the taking costs the night its reach — the wisp recoils to
; the far corner, so every life buys a whole fresh chase
; (leaving it beside the respawn made a catch strip every
; life in seconds once the draught learnt to hunt)
call restore_draught
ld a, DRAUGHT_COL0
ld (draught_col), a
ld a, DRAUGHT_ROW0
ld (draught_row), a
ld a, DRAUGHT_SPEED
ld (draught_timer), a
call save_draught
call draw_draught
ret
.gone:
call draw_lose_screen
call sting_nightfall
ld a, STATE_LOSE
ld (game_state), a
ret
; ----------------------------------------------------------------------------
; print_string / print_char — the machine's own letters. The Spectrum
; keeps its font in ROM: eight bytes per character, and FONT is chosen
; so that ASCII code x 8 + FONT is the glyph's address. Each character
; is drawn like any cell: attribute first, eight rows down the cell.
; ----------------------------------------------------------------------------
print_string:
.ps:
ld a, (hl)
cp $FF
ret z
push hl
push bc
call print_char
pop bc
pop hl
inc hl
inc c
jr .ps
print_char:
ld l, a
ld h, 0
add hl, hl
add hl, hl
add hl, hl
ld de, FONT
add hl, de
ex de, hl
push de
call attr_addr_cr
ld (hl), MSG_ATTR
call scr_addr_cr
pop de
ld b, 8
.pc:
ld a, (de)
ld (hl), a
inc de
inc h
djnz .pc
ret
; ----------------------------------------------------------------------------
; light_pip / draw_pips / draw_lives.
; ----------------------------------------------------------------------------
; light_pip — warm the next pip along and count the lamp. lit_count is
; the index of the pip to light AND the number of lamps lit so far —
; read it for the address, then step it.
light_pip:
ld a, (lit_count)
ld e, a
ld d, 0
inc a
ld (lit_count), a
ld hl, PIP_BASE
add hl, de
ld (hl), PIP_LIT
ret
; draw_pips — the tally row: one cell per lamp on the HUD ledge, all
; cold to start. A pip is pure attribute — no glyph, just a block of
; PAPER — so the row costs eight bytes of screen and no bitmap at all.
draw_pips:
ld hl, PIP_BASE
ld b, NUM_LAMPS
ld a, PIP_UNLIT
.dp:
ld (hl), a
inc hl
djnz .dp
ret
; draw_lives — three embers on the ledge's right shoulder.
draw_lives:
ld hl, LIFE_BASE
ld b, LIVES
ld a, LIFE_PIP
.dlv:
ld (hl), a
inc hl
djnz .dlv
ret
; ----------------------------------------------------------------------------
; draw_lamps — walk the position table: col, row pairs, $FF to finish.
; Placement is data; the drawing code neither knows nor cares how many
; lamps the town has tonight.
; ----------------------------------------------------------------------------
draw_lamps:
ld hl, lamp_data
.next:
ld a, (hl)
cp $FF
ret z
ld c, a
inc hl
ld b, (hl)
inc hl
push hl
call draw_lantern
pop hl
jr .next
; draw_lantern — an unlit lamp into cell (C, B): cold cyan attribute,
; then the lantern glyph down the cell like any texture.
draw_lantern:
call attr_addr_cr
ld (hl), LAMP_UNLIT
call scr_addr_cr
ld de, lantern
ld b, 8
.dlt:
ld a, (de)
ld (hl), a
inc de
inc h
djnz .dlt
ret
; ----------------------------------------------------------------------------
; scr_addr_cr — HL = bitmap address of cell (C, B)'s first pixel row.
; The row's top two bits pick the third of the screen (H), its bottom
; three become L's top bits, and the column fills L's low five.
; ----------------------------------------------------------------------------
scr_addr_cr:
ld a, b
and %00011000 ; the third (row bits 4-3) ...
or %01000000 ; ... under the screen base $40xx
ld h, a
ld a, b
and %00000111 ; the char row within the third ...
rrca ; ... rotated into bits 7-5
rrca
rrca
or c ; the column in bits 4-0
ld l, a
ret
; attr_addr_cr — HL = attribute address of cell (C, B):
; $5800 + row*32 + col, the row shifted up five times.
attr_addr_cr:
ld a, b
ld l, a
ld h, 0
add hl, hl
add hl, hl
add hl, hl
add hl, hl
add hl, hl
ld de, $5800
add hl, de
ld a, c
ld e, a
ld d, 0
add hl, de
ret
; wall_at — is cell (C, B) wall? The answer is already on the screen:
; every wall cell's attribute has WALL_BIT set, so one bit-test of
; attribute memory is the whole collision system. NZ = wall.
wall_at:
call attr_addr_cr
bit WALL_BIT, (hl)
ret
; ----------------------------------------------------------------------------
; The lamplighter's save / restore / draw.
; ----------------------------------------------------------------------------
; pos_bc — the lamplighter's cell into (C, B), read fresh from the data.
pos_bc:
ld a, (lamp_row)
ld b, a
ld a, (lamp_col)
ld c, a
ret
; save_under — copy the nine bytes of his cell into the buffer: eight
; bitmap rows, then the attribute. Runs as he ARRIVES, before the
; draw — so the buffer always holds true ground, never him.
save_under:
call pos_bc
call scr_addr_cr
ld de, under_lamp
ld b, 8
.su:
ld a, (hl)
ld (de), a
inc de
inc h
djnz .su
call pos_bc
call attr_addr_cr
ld a, (hl)
ld (under_lamp + 8), a
ret
; restore_under — the same nine bytes back the other way: the ground
; returns exactly as it was. Runs as he LEAVES, while the position
; still points at the old cell.
restore_under:
call pos_bc
call scr_addr_cr
ld de, under_lamp
ld b, 8
.ru:
ld a, (de)
ld (hl), a
inc de
inc h
djnz .ru
call pos_bc
call attr_addr_cr
ld a, (under_lamp + 8)
ld (hl), a
ret
draw_lamp:
; his colour first: the cell's attribute becomes his own —
; bright white on the black, his own light about him
call pos_bc
call attr_addr_cr
ld (hl), LAMP_ATTR
; then his shape, eight bytes down the cell like any texture
call pos_bc
call scr_addr_cr
ld de, lamplighter
ld b, 8
.dl:
ld a, (de)
ld (hl), a
inc de
inc h
djnz .dl
ret
; ----------------------------------------------------------------------------
; The draught's save / restore / draw — the lamplighter's engine, twice.
; Same loops, same nine-byte contract, its own buffer and its own
; position: two movers can share a world but never a buffer.
; ----------------------------------------------------------------------------
dpos_bc:
ld a, (draught_row)
ld b, a
ld a, (draught_col)
ld c, a
ret
save_draught:
call dpos_bc
call scr_addr_cr
ld de, under_draught
ld b, 8
.sd:
ld a, (hl)
ld (de), a
inc de
inc h
djnz .sd
call dpos_bc
call attr_addr_cr
ld a, (hl)
ld (under_draught + 8), a
ret
restore_draught:
call dpos_bc
call scr_addr_cr
ld de, under_draught
ld b, 8
.rd:
ld a, (de)
ld (hl), a
inc de
inc h
djnz .rd
call dpos_bc
call attr_addr_cr
ld a, (under_draught + 8)
ld (hl), a
ret
draw_draught:
call dpos_bc
call attr_addr_cr
ld (hl), DRAUGHT_ATTR
call dpos_bc
call scr_addr_cr
ld de, draught_glyph
ld b, 8
.dd:
ld a, (de)
ld (hl), a
inc de
inc h
djnz .dd
ret
; ----------------------------------------------------------------------------
; Data.
; ----------------------------------------------------------------------------
game_state:
defb STATE_TITLE
wall_ramp:
; The square warms in the game's own vocabulary: the stone
; stays dusk-blue; the lamplight catches the mortar first
; (ink white -> yellow), then the whole face glows BRIGHT.
; Never magenta — warmth is yellow here, not red-shifted blue.
defb %00001111 ; dusk stone, white mortar
defb %00001111
defb %00001111
defb %00001110 ; the mortar warms — yellow ink
defb %00001110
defb %00001110
defb %01001110 ; the stone catches the glow — BRIGHT
defb %01001110
defb %01110000 ; all eight lit: the square aglow —
; warm yellow stone, only at the win
lamp_data:
defb 4, 3
defb 27, 3
defb 9, 7
defb 22, 7
defb 6, 15
defb 25, 15
defb 13, 20
defb 18, 20
defb $FF
lamp_col:
defb START_COL
lamp_row:
defb START_ROW
tcol:
defb 0
trow:
defb 0
lit_count:
defb 0
lives:
defb LIVES
draught_col:
defb 28
draught_row:
defb 4
draught_timer:
defb 16
player_timer:
defb 0
seek_col:
defb 0
seek_row:
defb 0
dtcol:
defb 0
dtrow:
defb 0
under_lamp:
defb 0, 0, 0, 0, 0, 0, 0, 0, 0
under_draught:
defb 0, 0, 0, 0, 0, 0, 0, 0, 0
lamplighter:
defb %00111100
defb %00111100
defb %00011000
defb %01111110
defb %00011000
defb %00011000
defb %00100100
defb %01000010
lantern:
defb %00011000
defb %00100100
defb %01111110
defb %01111110
defb %01011010
defb %01111110
defb %01111110
defb %00111100
draught_glyph:
defb %00000000
defb %00111100
defb %01111110
defb %11111111
defb %11111111
defb %01111110
defb %00111100
defb %00000000
title_text:
defb "GLOAMING"
defb $FF
prompt_text:
defb "PRESS SPACE"
defb $FF
win_text:
defb "THE NIGHT IS HELD"
defb $FF
lose_text:
defb "NIGHT FALLS"
defb $FF
end start
Watch what start shrank to: black border, state to TITLE, draw the title, start the heartbeat, chime. Boot no longer knows anything about the game — not where the lamplighter stands, not how many lives, nothing. It knows how to open the door; the door knows how to begin. This is the refactor pattern from Unit 10 wearing structural clothes: there, we deleted code the world had made redundant; here, we moved code until each piece had exactly one owner. The screen proves nothing changed; the shape proves everything did.
When it’s wrong, see why
- One note, then silence, machine looks hung. The chime ran before
ei— its firstrestis halting for an interrupt that can’t arrive. Boot order: interrupts on, then anything that rests. - The title flashes past straight into the game. The SPACE test is inverted — bit 0 reads 1 when up;
ret nz(orjr nz, .twait) keeps waiting. Active-low, Unit 5’s oldest lesson, still collecting. - SPACE mid-game restarts the night.
title_stepis being called in every state — the dispatch must route only TITLE frames to it. A state machine is only as good as its gate. - Starting from the title gives a half-stale board. Something didn’t move into
init_game— every mutable byte the game touches must be re-established there, not left to adefbthat was only fresh at boot. (Unit 15’s warning aboutdefbinitial values, now with teeth.) - The game begins on its own after a win. The end states must hold — if WIN or LOSE frames fall through to
title_step, a held SPACE from your last input starts a game nobody asked for. Unit 20 handles returning deliberately.
Before and after
The unit began with a game that started without permission and ended with one that waits to be asked. Milestone 1 built every visible piece — screen, chime, key — and worked; milestone 2 changed nothing visible and mattered more: beginning went from an event in the boot sequence to a capability of the program, init_game, callable by anyone with a reason. The state machine now has its full shape — TITLE, PLAY, WIN, LOSE — with exactly one arrow missing: nothing yet leads back. One unit left.
Try this: dress the door
The title is two strings and a void, which means it’s cheap to art-direct. Recolour the name (write a different attribute in print_char’s path — or paint the title row’s attributes after printing: lamp-gold %01000110 reads beautifully on black). Move the rows. And add a third line — one more defb string, one more call — with a software house’s name on it. Every title screen of the era carried one, usually a bedroom coder’s invented label a good deal grander than the bedroom. Invent yours now: this won’t be the last title screen it appears on.
Try this: an impatient door
Make PRESS SPACE breathe: after printing, set FLASH on its cells — eleven attribute writes at row 14 — and the prompt pulses on the hardware’s own clock, no code per frame. The oldest attract-mode trick on the machine, and it costs nothing the loop ever sees.
Try this: any key to begin
Replace the SPACE read in title_step with Unit 7’s gather idiom — all three direction half-rows plus SPACE’s, OR’d together — so any key opens the door. Arcade-style. Then decide if you want it: a player resting their hand on QAOP at the title now starts before they meant to. Input design is choices, not just code.
What you’ve learnt
- A title screen is assembled from parts you had: the printer, the blackout, the beeper, one new phrase.
- Boot order can be audible — anything that rests on the heartbeat needs the heartbeat running first.
- The hardwired door works and can’t be reopened: preambles aren’t places.
init_gameturns beginning into a capability — state zero owns the waiting, the dispatch names each frame’s meaning.- A pure restructure can be the most important diff in a module: same bytes on screen, new shape underneath.
What’s next
Every screen in Gloaming now exists — title, play, gold, black — and they form a line, not a loop: win or lose, the game holds its final screen forever, one SPACE away from a title it can never reach. Unit 20 draws the last arrow: from either ending, back to a title that remembers your best night — and the module’s final lesson is the one every game ends on: what must be reborn, what may persist, and how a state machine closes.